tailieunhanh - Báo cáo khoa học: DYRK1A phosphorylates caspase 9 at an inhibitory site and is potently inhibited in human cells by harmine

DYRK1A is a member of the dual-specificity tyrosine-phosphorylation-reg-ulated protein kinase family and is implicated in Down’s syndrome. Here, we identify the cysteine aspartyl protease caspase9, a critical component of the intrinsic apoptotic pathway, as a substrate of DYRK1A. Depletion of DYRK1A from human cells by short interfering RNA inhibits the basal phosphorylation of caspase9 at an inhibitory site, Thr125. | ễFEBS Journal DYRK1A phosphorylates caspase 9 at an inhibitory site and is potently inhibited in human cells by harmine Anne Seifert Lindsey A. Allan and Paul R. Clarke BiomedicalResearch Institute College of Medicine Dentistry and Nursing University of Dundee UK Keywords apoptosis caspase DYRK harmine protein kinase Correspondence P. R. Clarke Biomedical Research Institute University of Dundee Level5 Ninewells Hospitaland Medical School Dundee DD1 9SY UK Fax 44 1382 669993 Tel 44 1382 425580 E-mail Received 28 August 2008 revised 8 October 2008 accepted 21 October 2008 doi DYRK1A is a member of the dual-specificity tyrosine-phosphorylation-regulated protein kinase family and is implicated in Down s syndrome. Here we identify the cysteine aspartyl protease caspase 9 a critical component of the intrinsic apoptotic pathway as a substrate of DYRK1A. Depletion of DYRK1A from human cells by short interfering RNA inhibits the basal phosphorylation of caspase 9 at an inhibitory site Thr125. DYRK1A-dependent phosphorylation of Thr125 is also blocked by harmine confirming the use of this b-carboline alkaloid as a potent inhibitor of DYRK1A in cells. We show that harmine not only inhibits the protein-serine threo-nine kinase activity of mature DYRK1A but also its autophosphorylation on tyrosine during translation indicating that harmine prevents formation of the active enzyme. When co-expressed in cells DYRK1A interacts with caspase 9 strongly induces Thr125 phosphorylation and inhibits caspase 9 auto-processing. Phosphorylation of caspase 9 by DYRK1A involves co-localization to the nucleus. These results indicate that DYRK1A sets a threshold for the activation of caspase 9 through basal inhibitory phosphorylation of this protease. Regulation of apoptosis through inhibitory phosphorylation of caspase 9 may play a role in the function of DYRK1A during development and in pathogenesis. DYRK1A is the most extensively .